20221221 has 4 divisors (see below), whose sum is σ = 26961632. Its totient is φ = 13480812.

The previous prime is 20221213. The next prime is 20221231. The reversal of 20221221 is 12212202.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20221221 - 2³ = 20221213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20221197 and 20221206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20221231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3370201 + ... + 3370206.

It is an arithmetic number, because the mean of its divisors is an integer number (6740408).

Almost surely, 2^20221221 is an apocalyptic number.

It is an amenable number.

20221221 is a deficient number, since it is larger than the sum of its proper divisors (6740411).

20221221 is an equidigital number, since it uses as much as digits as its factorization.

20221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6740410.

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 20221221 is about 4496.8011964062. The cubic root of 20221221 is about 272.4389044638.

Adding to 20221221 its reverse (12212202), we get a palindrome (32433423).

The spelling of 20221221 in words is "twenty million, two hundred twenty-one thousand, two hundred twenty-one".